﻿// Production steps of ECMA-262, Edition 5, 15.4.4.18
// Reference: http://es5.github.com/#x15.4.4.18
if(!Array.prototype.forEach) {
    Array.prototype.forEach = function(callback, thisArg) {
        var T, k;
        
        if(this === null) {
            throw new TypeError("this is null or not defined");
        }
        
        // 1. Let O be the result of calling ToObject passing the |this| value as the argument.
        var O = Object(this);
        
        // 2. Let lenValue be the result of calling the Get internal method of O with the argument "length".
        // 3. Let len be ToUint32(lenValue).
        var len = O.length >>> 0; // Hack to covert O.length to a UInt32
        
        // 4. If IsCallable(callback) is false, throw a TypeError exception.
        // See: http://es5.github.com/#x9.11
        if({}.toString.call(callback) != "[object Function]") {
            throw new TypeError(callback + " is not a function");
        }
        
        // 5. If thisArg was supplied, let T be thisArg; else let T be undefined.
        if(thisArg) {
            T = thisArg;
        }
        
        // 6. Let k be 0
        k = 0;
        
        // 7. Repeat, while k < len
        while(k < len) {
            
            var kValue;
            
            // a. Let Pk be ToString(k).
            //  This is implict for LHS operands of the in operator
            // b. Let kPresent be the result of calling the HasProperty internal method of O with argument Pk.
            //  This step can be combined with c
            // c. If kPresent is true, then
            if(k in O) {
                
                // i. Let kValue be the result of calling the Get internal method of O with argument Pk.
                kValue = O[k];
                
                // ii. Call the call internal method of callback with T as the this value and
                // argument list containing kValue, k, and O.
                callback.call(T, kValue, k, O);
            }
            // d. Increase k by 1.
            k++;
        }
        // 8. return undefined
    };
}